A. Markou

A highly segmented NaI(Tl) detector with vacuum photodiode readout for measuring electromagnetic showers at the CERN ISR

Abstract In this report we describe construction and performance of two identical units of electromagnetic shower counters which were installed in the axial-field spectrometer at the CERN-ISR in 1982 to provide improved detection of photons and electrons over a 1.3 sr solid angle of the AFS calorimeter. Thallium doped sodium-iodide in the form of small blocks served as an active shower material. Vacuum photodiodes and low-noise charge sensitive electronics were used for the deposited energy measurement and signal amplification. The stable performance of the detectors over a period of more than 18 months until the closure of the ISR has proven that vacuum photodiodes can reliably be utilized in highly modularized large scale detectors operating in a high magnetic field environment.

A large aperture spectrometer at Fermilab to study high mass dimuons

A large acceptance forward spectrometer located in a unique antiproton enriched beam has been used at Fermi National Accelerator Laboratory by Experiment 537 to study the production of high mass muon pairs. When the beam was operated at a momentum of 125 GeV/c, it had a flux of 1.5 × 107 particles per second of which 18% were antiprotons. The spectrometer was of closed geometry design and used drift chambers as the tracking elements. Operating over a relatively short period, the experiment accumulated the largest sample of antiproton-induced high mass dimuons of any experiment to date. The contamination of this data by pion-induced dimuons was less than 0.5%.